More than a million people in the U.S. have severely impaired vision. Their visual impairments are diverse and there is only limited understanding of how these impairments affect performance of tasks of daily life such as walking and reading. The NEI and several workshops sponsored by it have identified a need for research on the visual requirments of everyday tasks. I propose to determine the degree of visual restriction of several types which can be tolerated before mobility is impaired. Normal subjects will wear goggles which restrict vision in various ways (field restriction, contrast reduction, spatial-frequency cutoff) and to various degrees, and will be asked to walk down a long cluttered corridor as quickly as they can without touching any of the obstacles. I will measure their performance (total time, and number of contacts with obstacles) as a function of visual restriction. The results will tell us the visual requirements of the task in terms of visual field width, contrast, and spatial-frequency cutoff. Of the three types of restriction, two (field restriction and contrast reduction) should be good simulations of common visual impairments, and two (contrast reduction and spatial-frequency cutoff) manipulate variables which play central roles in current theories of vision. After analysis, the results will define the visual requirements of a walking task and the predictive value (for this task) of characterizing residual vision by acuity, field, and contrast sensitivity function.